The present invention relates to a lifting anchor for embedding into prefabricated concrete panels at the time of forming the panels; ie., at the time the concrete is poured into the panel mold. The invention is especially adapted for use in a prefabricated panel forming process where the concrete forming mold may be many hundreds of feet in length, and the mold is movable relative to a concrete pouring station. After curing, such prefabricated panels are typically cut into predetermined lengths to provide individual prefabricated panels for delivery to a job site. At the job site, each individual panel is then lifted to a vertical position, and aligned next to an adjacent vertically-positioned panel, to construct a concrete wall. The present invention provides an anchor to facilitate the lifting operation at the job site.
The continuous-mold practice of pouring a considerable length of concrete into a moving mold creates a requirement regarding the proper positioning of the lifting anchors which later will be used on the job site to lift each of the panel sections. The anchors are embedded into the concrete at the time of pouring and curing of the concrete, and each of the lifting anchors must be positioned adjacent a cut line so that the lifting anchor can be accessible, after the panel has been cut to the proper length, to be connected to a lifting device.
At the time of pouring, specifications are available to set the length of each of the prefabricated panels which ultimately are to be cut from the molded concrete sheet, and so the distances can be measured from one end of the concrete mold to place the anchors in the mold at predetermined spaced positions corresponding to the eventual lengths of each of the cut panels. However, overall system measurement tolerances may be cumulative, and therefore when literally dozens of measurements are made in an end-to-end fashion in an elongated concrete mold it is possible that the measured positions of the anchors in the mold may vary by as much as several inches from the specified positions in the final panel.
Later, when the elongated concrete sheet is cut into sections, it is imperative that the lifting anchors be exposed at the cut ends so that the panels can be properly raised. Two scenarios can be visualized: 1) the anchors are embedded into the concrete at too great a distance from the cut end, and therefore they cannot be accessed for lifting; or 2) the anchors are embedded into the concrete beyond the cut end position, and therefore the concrete-cutting saw not only cuts the concrete but also cuts the anchors and renders them useless.
The present invention provides a convenient solution to the above-described problems, and provides a novel construction for concrete anchors of the type described herein.
Reference may be made to U.S. Pat. No. 5,649,782, and U.S. Design Pat. No. D272,517 for examples of other and different types of panel lifting anchors. The design patent shows an eyelet structure affixed to two reinforcing bars which are embedded into the concrete at the time the prefabricated panels are formed, where the eyelet structure is protected from concrete immersion by some type of removable plug, and after the curing process the plug may be removed to provide access to the eyelet to provide a lifting anchor. The utility patent shows a female threaded member which is affixed to a reinforcing bar, and both members are embedded into the concrete at the time the prefabricated panels are formed; after curing, a threaded lifting loop may be inserted into the female member.